太湖及与湖岸城市间大气颗粒物分布特征分析

利用冬季连续2 d在两种气象条件下分别环绕太湖对湖泊近无锡区域、湖心区域、近西山岛区域和近苏州区域近湖层的PM0.5、PM2.5和PM10进行质量浓度观测,并通过分析同期相应气象资料(包括高空和地面风场、流场以及湖面站点的水平垂直风向风速等气象数据),探讨湖泊区域内外颗粒物浓度变化的时空特征以及受气象条件变化的影响。研究表明:第1天当天气为晴转阴且无雾时,由于湖面本身缺乏密集强排放源,以及因湖面大气上升运动较强使颗粒物容易被扩散稀释,且受偏东转东南气流所带来的气团较干净影响,湖面湖心区域和离岛区域颗粒物浓度明显低于上游城市;而在第2天当天气为雾时情况则相反,由于湖面大气较弱的上升运动使得大气颗粒物不容易被扩散稀释,且湖泊强大的水汽源影响有助于气溶胶和颗粒物的生成进而使得湖面颗粒物浓度大于周围城市。此外还发现在两种天气下,颗粒物浓度都存在无锡区域最高,湖心区域次之,苏州区域较低的特征。并且,在雾天不同粒径颗粒物间变化的相关系数更高。

Characteristics analysis on distribution of particulate matters between lake shore cities and Taihu Lake

Based on the concentration observation data of PM_0.5, PM_2.5 and PM₁₀ on surface layer of four areas in Taihu lake as Wuxi, Xishan island, Suzhou, and the central lake area in two days within two kinds of meteorological parameters. Moreover, through analyzing the corresponding meteorological data in the same period including wind field, flow field and horizontal, vertical wind direction and speed, the spatial-temporal variation characteristics of particles in Taihu lake and the influence of meteorological parameters were discussed. Results show that in sunny but cloudy day without fog, the particulate concentration in the lake area and outlying island regions are significantly lower than that in the city, it is because the particles would be easily to spread and dilute by ascending motion. Meanwhile, there is no strong emission on lake and the air flow from the east and the southeast will bring purer air mass; while in foggy day, under the static and stable meteorological condition with weak ascending motion, the strong vapor source of lake and stable weather condition facilitates the genesis and accumulation of aerosol and particles, which makes the different condition compared with the day without fog. In addition, the feature of spatial variation of particle concentration is characterized as follows:it is the highest in lake near Wuxi area, it is higher in the central lake than that near Suzhou area. The correlation coefficient of concentration among three sizes of particles is the highest in foggy day.